i have a 88 cherokee 4.0 and auto my problem is it back fires through the throttle body and when trying to drive it it wont take fuel good plus i cant plug the vacume line up to the map sensor or it runs even worse i have replaced the following crank sensor,tps sensor,plugs,wires,cap,rotor button,checed injectors,replaced head gasket had head job done,intake gasket, what else is there i am lost????? any and all help greatly appreciated

 

when it back fires threw the throttle body its a timing issue. its sparking with the intake valves open. It sounds like the spark plug wires are not on the correct cylender, and timing is off. this is where i would start.

 

Thing should run like total crap and die without the map vacuum hooked up.

 

Agree with Gorilla... Since you changed your wires, check to make sure they are placed correctly. Also check your cap alignment. Something is firing out of order.

Greg

 

thanks guys i have cheched my wires again and they are right.im lost !! i cant figure it out i have even reset the distributor and no change its still doing the same thing.

 

Test your fuel pressure. Unfortunately many people associate backfiring with a rich mixture or as an electrical issue when a lean condition can really be the cause.

 

also double check your cap and rotor to make sure everything is right....look for carbon trace (small lines) in the cap and see if the electrodes have any burn marks on them....make sure you have the right rotor...I had a bad experience one time from the wrong parts, that looked like they were right